linux-kernel - [PATCH v3] media: em28xx: add missing em28xx_close

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Message-Id: <20210729202333.21605-1-paskripkin@gmail.com>
Date:   Thu, 29 Jul 2021 23:23:33 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     mchehab@...nel.org, hverkuil@...all.nl
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        syzbot+a6969ef522a36d3344c9@...kaller.appspotmail.com
Subject: [PATCH v3] media: em28xx: add missing em28xx_close_extension

If em28xx dev has ->dev_next pointer, we need to delete ->dev_next list
node from em28xx_extension_devlist on disconnect to avoid UAF bugs and
corrupted list bugs, since driver frees this pointer on disconnect.

Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
Reported-and-tested-by: syzbot+a6969ef522a36d3344c9@...kaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---

Changes in v3:
	Changed order of em28xx_close_extension() and
	em28xx_release_resources() as Hans suggested

Changes in v2:
	Previous patch was completely broken. I've done some debugging
	again and found true root case of the reported bug.

---
 drivers/media/usb/em28xx/em28xx-cards.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
index c1e0dccb7408..948e22e29b42 100644
--- a/drivers/media/usb/em28xx/em28xx-cards.c
+++ b/drivers/media/usb/em28xx/em28xx-cards.c
@@ -4139,8 +4139,11 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
 
 	em28xx_close_extension(dev);
 
-	if (dev->dev_next)
+	if (dev->dev_next) {
+		em28xx_close_extension(dev->dev_next);
 		em28xx_release_resources(dev->dev_next);
+	}
+
 	em28xx_release_resources(dev);
 
 	if (dev->dev_next) {
-- 
2.32.0